In microbiological processes related to soil remediation the destruction of organic pollutants by microorganisms is furthered by the cultivation and selection of specialized microorganisms with the objective of an improved performance (mutagenesis with predominantly chemical mutagens) which thereafter are fed back into the ground. The central problem of mutagenesis is that mutagenesis can only be controlled during the stage of cultivation. Once the microorganisms are fed back into the ground, ongoing mutagenesis in soils is almost impossible to control. An uncontrolled mutagenesis in a milieu of pollutants, such as pigments, solvents, pesticides etc. can produce mutants, which might be carcinogenic and/or embryotoxic and/or pathogenic.
A second problem is encountered in soil areas where pathogenic microorganisms can be expected to an increased extent. Reference is made to plants disposing of animal bodies, tanneries, and fur treatment plants which are already affected by pathogenic microorganisms such as the anthrax (Bacillus anthracis) as well as to abattoirs and farms. In these cases, the problem arises because during microbiological remediation of pollutants the growth of pathogenic microorganisms also simultaneously furthered.
A third problem area can be identified in the United States, England, and Russia where in the context of the biological warfare large-scale field tests have been carried out using extremely dangerous pathogens such as the anthrax (Bacillus anthracis), which render vast areas uninhabitable.
A fourth problem area arises from those substances produced by the activity of microorganisms such as metabolites and organic substances resulting from biosynthesis such substances frequently are more toxic than the pollutants found in the soil before treatment. The majority of these substances tend to be persistent and cannot be decomposed by microorganisms. Classic metabolites are for example aflatoxines, a group of metabolites produced by molds which are highly toxic and, moreover, are carcinogenic, as well as cyano-compounds, originating from Cyanophyceae, a group of about 2,000 one-celled algae.
A fifth problem area is represented by man-made pollution of soils and the ground water with organic substances.
A sixth problem area arises from a variety of insoluble inorganic substances such as mercury sulfide, red lead or arsenic trioxide which cannot be removed from the soil or the ground water by traditional methods or can only be removed at an extremely high cost.
The present invention can be considered based on the following prior art. Preparatory research and development has been performed by the immunochemistry in the course of the production and sterilization of sera. The basis of this research and development is electrolysis, i.e. the transportation of an electrolyte through a semipermeable membrane. As to electrodialysis, in general two diaphragms are required which enclose a central chamber containing a colloidal solution to be treated, whereas the electrodes are placed in the outer chambers. On the latter basis, German Patent No. DE 383 491 (Elektroosmose AG) discloses an arrangement comprising three chambers and electrodes of approx. 400 cm.sup.2 which are intended to sterilize liquids or solids, the latter being saturated with a solution of sodium chloride, within 2 hours at a current of 10-12 A and a direct voltage of 60 V. In this apparatus, streptococci, staphylococci and pneumococci have been sterilized. Similar apparatus have also been applied in the German Patents DE 397 888, DE 150 328, DE 397 551, and DE 423 822. In these aforementioned patents the electric current was employed to cause the sterilization. The German Patents Nos. DE 463 333 and DE 383 481, however, evidenced that the effect of sterilization is not based on the effects of the electric current but on the effects of the weak hydrochloric acid generated by the dissociation of the solution of sodium chloride. An application of aforesaid techniques to the treatment of soils and/or the ground water are not yet known.
As to the remediation of soils, electrokinetic processes using two or more electrodes are described in U.S. Pat. Nos. 5,137,608 and 5,074,986, as well as in the European Patent EP 0 312 174 and in the German Patent DE 39 20 342. By the aforesaid electrokinetic processes pollutants such as soluble heavy metal compounds, and some polar organic substances, such as phenol, are simply transported to the electrodes. Most of the inorganic compounds will precipitate on the electrodes while the organic substances will accumulate close to the electrodes or be converted by electrode reactions.
This invention, however, by applying techniques such as pole reversal of the electric field and a low density of current, will prevent electrokinetic transportation of pollutants through the soil. Instead, the pollutants are treated in situ, i.e. mineralized by non-Faraday processes.
In my earlier U.S. Pat. No. 5,595,644, a process is described by which harmful materials are caused to decompose in situ by the generation of an ionization channel between electrodes via application of a voltage in the ground region so as to increase the conductivity of the ground region affected. The electric voltage is regulated by adjusting the current such that the energy supplied is equal to or greater than the electron affinity of the atoms making up the harmful materials in the treated ground region. In accordance with this patent, the harmful substances undergo oxidation by electron reactions.
In the German patent application No. DE 43 15 248, another method for the decontamination of soils has been described. Electrolytes are fed into the soil enabling electrolysis in combination with another electrolyte which, in the electric field between electrodes, produce ions that on their part will react with the pollutants so as to convert the pollutants into harmless substances.
Further prior art processes relate to electrochemical decomposition of pollutants in apparatus and equipment, such as indicated in the German patent applications DE 40 07 805, DE 36 00 772 or DE 40 13 068.